fix for all wierd crashes happening to lltexturecache.cpp, cuased by running viewer 2.0 and viewer 1.23 at the same time. Specifically for the following jiras:

EXT-6692: crash at LLTextureCache::readEntryFromHeaderImmediately [secondlife-bin lltexturecache.cpp:1145]
EXT-6691: crash at LLTextureCache::writeEntryToHeaderImmediately [secondlife-bin lltexturecache.cpp:1126]
possible fix for EXT-6567: crash at LLImageBase::allocateData [secondlife-bin llimage.cpp:170]

4 files changed, 77 insertions, 21 deletions

diff --git a/indra/newview/llappviewer.cpp b/indra/newview/llappviewer.cpp
index 11c252406a..cdd553b9b4 100644
--- a/indra/newview/llappviewer.cpp
+++ b/indra/newview/llappviewer.cpp
@@ -3000,9 +3000,36 @@ void LLAppViewer::migrateCacheDirectory()
 #endif // LL_WINDOWS || LL_DARWIN
 }
 
+//static
+S32 LLAppViewer::getCacheVersion() 
+{
+	static const S32 cache_version = 7;
+
+	return cache_version ;
+}
+
 bool LLAppViewer::initCache()
 {
 	mPurgeCache = false;
+	BOOL disable_texture_cache = FALSE ;
+	BOOL read_only = mSecondInstance ? TRUE : FALSE;
+	LLAppViewer::getTextureCache()->setReadOnly(read_only) ;
+
+	if (gSavedSettings.getS32("LocalCacheVersion") != LLAppViewer::getCacheVersion()) 
+	{
+		if(read_only) 
+		{
+			disable_texture_cache = TRUE ; //if the cache version of this viewer is different from the running one, this viewer can not use the texture cache.
+		}
+		else
+		{
+			mPurgeCache = true; // Purge cache if the version number is different.
+			gSavedSettings.setS32("LocalCacheVersion", LLAppViewer::getCacheVersion());
+		}
+	}
+
+	if(!read_only)
+	{
 	// Purge cache if user requested it
 	if (gSavedSettings.getBOOL("PurgeCacheOnStartup") ||
 		gSavedSettings.getBOOL("PurgeCacheOnNextStartup"))
@@ -3010,16 +3037,6 @@ bool LLAppViewer::initCache()
 		gSavedSettings.setBOOL("PurgeCacheOnNextStartup", false);
 		mPurgeCache = true;
 	}
-	// Purge cache if it belongs to an old version
-	else
-	{
-		static const S32 cache_version = 6;
-		if (gSavedSettings.getS32("LocalCacheVersion") != cache_version)
-		{
-			mPurgeCache = true;
-			gSavedSettings.setS32("LocalCacheVersion", cache_version);
-		}
-	}
 	
 	// We have moved the location of the cache directory over time.
 	migrateCacheDirectory();
@@ -3034,6 +3051,7 @@ bool LLAppViewer::initCache()
 		gSavedSettings.setString("CacheLocation", new_cache_location);
 		gSavedSettings.setString("CacheLocationTopFolder", gDirUtilp->getBaseFileName(new_cache_location));
 	}
+	}
 	
 	if (!gDirUtilp->setCacheDir(gSavedSettings.getString("CacheLocation")))
 	{
@@ -3042,7 +3060,7 @@ bool LLAppViewer::initCache()
 		gSavedSettings.setString("CacheLocationTopFolder", "");
 	}
 	
-	if (mPurgeCache)
+	if (mPurgeCache && !read_only)
 	{
 		LLSplashScreen::update(LLTrans::getString("StartupClearingCache"));
 		purgeCache();
@@ -3052,13 +3070,12 @@ bool LLAppViewer::initCache()
 	
 	// Init the texture cache
 	// Allocate 80% of the cache size for textures
-	BOOL read_only = mSecondInstance ? TRUE : FALSE;
 	const S32 MB = 1024*1024;
 	S64 cache_size = (S64)(gSavedSettings.getU32("CacheSize")) * MB;
 	const S64 MAX_CACHE_SIZE = 1024*MB;
 	cache_size = llmin(cache_size, MAX_CACHE_SIZE);
 	S64 texture_cache_size = ((cache_size * 8)/10);
-	S64 extra = LLAppViewer::getTextureCache()->initCache(LL_PATH_CACHE, texture_cache_size, read_only);
+	S64 extra = LLAppViewer::getTextureCache()->initCache(LL_PATH_CACHE, texture_cache_size, disable_texture_cache);
 	texture_cache_size -= extra;
 
 	LLSplashScreen::update(LLTrans::getString("StartupInitializingVFS"));
diff --git a/indra/newview/llappviewer.h b/indra/newview/llappviewer.h
index a915b7fa50..60645c46d4 100644
--- a/indra/newview/llappviewer.h
+++ b/indra/newview/llappviewer.h
@@ -102,6 +102,8 @@ public:
 	static LLImageDecodeThread* getImageDecodeThread() { return sImageDecodeThread; }
 	static LLTextureFetch* getTextureFetch() { return sTextureFetch; }
 
+	static S32 getCacheVersion() ;
+
 	const std::string& getSerialNumber() { return mSerialNumber; }
 	
 	bool getPurgeCache() const { return mPurgeCache; }
diff --git a/indra/newview/lltexturecache.cpp b/indra/newview/lltexturecache.cpp
index 7a0712f8aa..290ac8dc04 100644
--- a/indra/newview/lltexturecache.cpp
+++ b/indra/newview/lltexturecache.cpp
@@ -742,7 +742,7 @@ LLTextureCache::LLTextureCache(bool threaded)
 	  mHeaderMutex(NULL),
 	  mListMutex(NULL),
 	  mHeaderAPRFile(NULL),
-	  mReadOnly(FALSE),
+	  mReadOnly(TRUE), //do not allow to change the texture cache until setReadOnly() is called.
 	  mTexturesSizeTotal(0),
 	  mDoPurge(FALSE)
 {
@@ -929,13 +929,16 @@ U32 LLTextureCache::sCacheMaxEntries = MAX_REASONABLE_FILE_SIZE / TEXTURE_CACHE_
 S64 LLTextureCache::sCacheMaxTexturesSize = 0; // no limit
 const char* entries_filename = "texture.entries";
 const char* cache_filename = "texture.cache";
-const char* textures_dirname = "textures";
+const char* old_textures_dirname = "textures";
+//change the location of the texture cache to prevent from being deleted by old version viewers.
+const char* textures_dirname = "texturecache";
 
 void LLTextureCache::setDirNames(ELLPath location)
 {
 	std::string delem = gDirUtilp->getDirDelimiter();
-	mHeaderEntriesFileName = gDirUtilp->getExpandedFilename(location, entries_filename);
-	mHeaderDataFileName = gDirUtilp->getExpandedFilename(location, cache_filename);
+
+	mHeaderEntriesFileName = gDirUtilp->getExpandedFilename(location, textures_dirname, entries_filename);
+	mHeaderDataFileName = gDirUtilp->getExpandedFilename(location, textures_dirname, cache_filename);
 	mTexturesDirName = gDirUtilp->getExpandedFilename(location, textures_dirname);
 }
 
@@ -947,15 +950,37 @@ void LLTextureCache::purgeCache(ELLPath location)
 	{
 		setDirNames(location);
 		llassert_always(mHeaderAPRFile == NULL);
-		LLAPRFile::remove(mHeaderEntriesFileName, getLocalAPRFilePool());
-		LLAPRFile::remove(mHeaderDataFileName, getLocalAPRFilePool());
+
+		//remove the legacy cache if exists
+		std::string texture_dir = mTexturesDirName ;
+		mTexturesDirName = gDirUtilp->getExpandedFilename(location, old_textures_dirname);
+		if(LLFile::isdir(mTexturesDirName))
+		{
+			std::string file_name = gDirUtilp->getExpandedFilename(location, entries_filename);
+			LLAPRFile::remove(file_name, getLocalAPRFilePool());
+
+			file_name = gDirUtilp->getExpandedFilename(location, cache_filename);
+			LLAPRFile::remove(file_name, getLocalAPRFilePool());
+
+			purgeAllTextures(true);
+	}
+		mTexturesDirName = texture_dir ;
 	}
+
+	//remove the current texture cache.
 	purgeAllTextures(true);
 }
 
-S64 LLTextureCache::initCache(ELLPath location, S64 max_size, BOOL read_only)
+//is called in the main thread before initCache(...) is called.
+void LLTextureCache::setReadOnly(BOOL read_only)
 {
 	mReadOnly = read_only;
+}
+
+//called in the main thread.
+S64 LLTextureCache::initCache(ELLPath location, S64 max_size, BOOL disable_texture_cache)
+{
+	llassert_always(getPending() == 0) ; //should not start accessing the texture cache before initialized.
 	
 	S64 header_size = (max_size * 2) / 10;
 	S64 max_entries = header_size / TEXTURE_CACHE_ENTRY_SIZE;
@@ -968,6 +993,15 @@ S64 LLTextureCache::initCache(ELLPath location, S64 max_size, BOOL read_only)
 		sCacheMaxTexturesSize = max_size;
 	max_size -= sCacheMaxTexturesSize;
 	
+	if(disable_texture_cache) //the texture cache is disabled
+	{
+		llinfos << "The texture cache is disabled!" << llendl ;
+		setReadOnly(TRUE) ;
+		purgeAllTextures(true); 
+
+		return max_size ;
+	}
+
 	LL_INFOS("TextureCache") << "Headers: " << sCacheMaxEntries
 			<< " Textures size: " << sCacheMaxTexturesSize/(1024*1024) << " MB" << LL_ENDL;
 
@@ -986,6 +1020,8 @@ S64 LLTextureCache::initCache(ELLPath location, S64 max_size, BOOL read_only)
 	readHeaderCache();
 	purgeTextures(true); // calc mTexturesSize and make some room in the texture cache if we need it
 
+	llassert_always(getPending() == 0) ; //should not start accessing the texture cache before initialized.
+
 	return max_size; // unused cache space
 }
 
diff --git a/indra/newview/lltexturecache.h b/indra/newview/lltexturecache.h
index ca8815ee7e..5dc06ff401 100644
--- a/indra/newview/lltexturecache.h
+++ b/indra/newview/lltexturecache.h
@@ -110,7 +110,8 @@ public:
 	/*virtual*/ S32 update(U32 max_time_ms);	
 	
 	void purgeCache(ELLPath location);
-	S64 initCache(ELLPath location, S64 maxsize, BOOL read_only);
+	void setReadOnly(BOOL read_only) ;
+	S64 initCache(ELLPath location, S64 maxsize, BOOL disable_texture_cache);
 
 	handle_t readFromCache(const std::string& local_filename, const LLUUID& id, U32 priority, S32 offset, S32 size,
 						   ReadResponder* responder);